THE DETECTION AND MEASUREMENT OF MECHANICAL STRAIN DEFLECTION IN HOSTILE ENVIRONMENTS, INCLUDING HIGH PRESSURES AND TEMPERATURES, ARE LIMITED USING STANDARD INSTRUMENTATION. A METHOD FOR OVERCOMING THESE LIMITATIONS WILL BE STUDIED USING NUCLEAR GAMMA RAY RESONANCE, COMMONLY CALLED THE "MOSSBAUER EFFECT," TO MEASURE STRAIN RATES. PRELIMINARY STUDIES WILL BE CONCENTRATED ON DEVELOPING GAMMA SOURCE COUNTING CONFIGURATIONS ON ROOM-TEMPERATURE UNIAXIAL AND BIAXIAL (THIN-WALLED TUBE) STRAINS USING SOURCES SUCH AS FE57 AND CO57. THE SENSITIVITIES OF STRAIN-RATE MEASUREMENT WILL BE ESTABLISHED, AND THE EFFECTS OF ELEVATED TEMPERATURES ON THE EMITTING SOURCE AND/OR ABSORBER AND DETECTOR PERFORMANCE WILL BE EVALUATED. THIS METHOD CAN BE READILY APPLIED TO BIAXIAL, SLOW-MOVING ("CREEP") STRAINS SUCH AS THOSE EXPERIENCED IN HIGH-TEMPERATURE NUCLEAR REACTOR SYSTEMS, COOLANT-BOUNDARY SURFACES.